A football starlet who saw his career wrecked by a high tackle from a former Boro player had “no guarantees” of a career in the game, a court heard.

Ben Collett, then aged 18, had his right leg broken in two places by Boro’s Gary Smith while playing in only his first reserve team game for Manchester United in 2003.

He was awarded £4.3m in damages last August against Boro and Smith.

But both the club and Smith, who now plays for Brentford, have challenged the size of the award at a hearing at the Civil Courts of Justice in Manchester.

Andrew Prynne QC argued to a panel of three appeal judges yesterday that Collett might not have made it in the Premier League and might have instead become a Championship footballer.

He also suggested the amount of the award had over-estimated Collett’s earning potential if he had gone on to play in either of the top two divisions. Mr Prynne said there were no guarantees and great uncertainties for young footballers in the game.

Both Smith and Boro had admitted liability for the ‘‘negligent’’ tackle. But Mr Prynne said it was wrong of the judge, Mrs Justice Swift, to base her estimation of the award on players’ wages continuously going up.

The appeal judges must now decide whether the size of the award is to be reduced although ultimately the money will be paid by Boro’s insurers.